Which early Frankish king brought the separate Frankish groups under a single rule and became a Christian?

Explication

The king meant here ruled around the turn of the sixth century, joining groups that had been led separately under one crown and accepting Christian baptism, long before the Frankish realm became an empire. Charlemagne is the closest trap, because he is the better-known Frankish ruler, but he lived some two and a half centuries later and inherited a kingdom that was already united and already Christian.